Imaging lens comprising five lenses of +-0+- refractive powers

ABSTRACT

There is provided an imaging lens with excellent optical characteristics which satisfies demand of the wide field of view, the low-profileness and the low F-number. An imaging lens comprises, in order from an object side to an image side, a first lens having a convex surface facing the object side and positive refractive power near an optical axis, a second lens having negative refractive power near the optical axis, a third lens having aspheric surfaces on both sides, a fourth lens, and a fifth lens having a concave surface facing the image side and the negative refractive power near the optical axis, wherein an image-side surface of said fifth lens is formed as an aspheric surface having at least one pole point in a position off the optical axis, and predetermined conditional expressions are satisfied.

The present application is based on and claims priority of a Japanesepatent application No. 2018-142118 filed on Jul. 30, 2018, the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an imaging lens which forms an image ofan object on a solid-state image sensor such as a CCD sensor or a C-MOSsensor used in an imaging device, and more particularly relates to animaging lens which is built in a smartphone and a mobile phone whichbecome increasingly compact and excellent in performance, an informationterminal such as a PDA (Personal Digital Assistant), a game console, PCand a robot, and moreover, a home appliance with camera function, amonitoring camera and an automobile.

Description of the Related Art

In recent years, it becomes common that camera function is mounted in ahome appliance, information terminal equipment, an automobile and publictransportation. Demand of products with the camera function is moreincreased, and development of various products is being madeaccordingly.

The imaging lens mounted in such equipment is required to be compact andto have high-resolution performance.

As a conventional imaging lens aiming high performance, for example, theimaging lens disclosed in Patent Document 1 has been known.

Patent Document 1 (JP Patent 6228305) discloses an imaging lenscomprising, in order from an object side to an image side, a first lenswith positive refractive power having a convex surface facing the objectside, a second lens with negative refractive power having a concavesurface facing the image side, a third lens with refractive power, afourth lens with the refractive power, and a fifth lens with thenegative refractive power, wherein a combination lens of said third lensand said fourth lens has negative refractive power.

SUMMARY OF THE INVENTION

However, in lens configurations disclosed in the Patent Document 1, whenwide field of view, low-profileness and low F-number are to be realized,it is very difficult to correct aberrations at a peripheral area, andexcellent optical performance can not be obtained.

The present invention has been made in view of the above-describedproblems, and an object of the present invention is to provide animaging lens with high resolution which satisfies demand of the widefield of view, the low-profileness and the low F-number in well balanceand excellently corrects aberrations.

Regarding terms used in the present invention, “a convex surface”, “aconcave surface” or “a plane surface” of lens surfaces implies that ashape of the lens surface near an optical axis (paraxial portion).“Refractive power” implies the refractive power near the optical axis.“A pole point” implies an off-axial point on an aspheric surface atwhich a tangential plane intersects the optical axis perpendicularly. “Atotal track length” is defined as a distance along the optical axis froman object-side surface of an optical element located closest to theobject to an image plane. “The total track length” and “a back focus” isa distance obtained when thickness of an IR cut filter or a cover glasswhich may be arranged between the imaging lens and the image plane isconverted into an air-converted distance.

An imaging lens according to the present invention comprises, in orderfrom an object side to an image side, a first lens having a convexsurface facing the object side and positive refractive power near anoptical axis, a second lens having negative refractive power near theoptical axis, a third lens having aspheric surfaces on both sides, afourth lens, and a fifth lens having a concave surface facing the imageside and the negative refractive power near the optical axis, wherein animage-side surface of the fifth lens is formed as an aspheric surfacehaving at least one pole point in a position off the optical axis.

According to the imaging lens having the above-described configuration,the first lens properly corrects spherical aberration and distortion byhaving the convex surface facing the object side near the optical axis.The second lens properly corrects the spherical aberration and chromaticaberration occurring at the first lens. The third lens properly correctsaberrations at a peripheral area by the aspheric surfaces on both sides.The fourth lens properly corrects astigmatism, field curvature and thedistortion. The fifth lens properly corrects the chromatic aberration,the astigmatism, the field curvature and the distortion. An image-sidesurface of the fifth lens is a concave surface facing the image sidenear the optical axis, and the field curvature and the distortion can bemore properly corrected and a light ray incident angle to an imagesensor can be properly controlled by forming as the aspheric surfacehaving at least one pole point in a position off the optical axis.

According to the imaging lens having the above-described configuration,it is preferable that an image-side surface of the first lens is aconcave surface facing the image side near the optical axis.

When the image-side surface of the first lens is the concave surfacefacing the image side near the optical axis, the astigmatism and thedistortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that an object-side surface and an image-side surfaceof the third lens are formed as plane surfaces near the optical axis.

When the object-side surface and the image-side surface of the thirdlens are plane surfaces near the optical axis, the astigmatism, thefield curvature and the distortion at the peripheral area can beproperly corrected by the aspheric surfaces on both sides withoutaffecting a focal length of an overall optical system of the imaginglens.

According to the imaging lens having the above-described configuration,it is preferable that the fourth lens has the positive refractive powernear the optical axis.

When the refractive power of the fourth lens is positive, thelow-profileness is more facilitated.

According to the imaging lens having the above-described configuration,it is preferable that an object-side surface of the fourth lens is aconcave surface facing the object side near the optical axis.

When the object-side surface of the fourth lens is the concave surfacefacing the object side near the optical axis, the astigmatism, the fieldcurvature and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that an object-side surface of the fifth lens is aconvex surface facing the object side near the optical axis.

When the object-side surface of the fifth lens is the convex surfacefacing the object side near the optical axis, the astigmatism and thedistortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (1) is satisfied:0.70<vd3/vd4<1.30  (1)

where

vd3: an abbe number at d-ray of the third lens, and

vd4: an abbe number at d-ray of the fourth lens.

The conditional expression (1) defines an appropriate range of the abbenumbers at d-ray of the third lens and the fourth lens. By satisfyingthe conditional expression (1), the chromatic aberration can be properlycorrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (2) is satisfied:0.40<r2/f<1.20  (2)

where

r2: paraxial curvature radius of an image-side surface of the firstlens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (2) defines an appropriate range of theparaxial curvature radius of the image-side surface of the first lens.When a value is below the upper limit of the conditional expression (2),the astigmatism can be properly corrected. On the other hand, when thevalue is above the lower limit of the conditional expression (2), thespherical aberration can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (3) is satisfied:2.20<r9/f<6.00  (3)

where

r9: paraxial curvature radius of an object-side surface of the fifthlens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (3) defines an appropriate range of theparaxial curvature radius of the object-side surface of the fifth lens.When a value is below the upper limit of the conditional expression (3),the field curvature can be properly corrected. On the other hand, whenthe value is above the lower limit of the conditional expression (3),the astigmatism and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (4) is satisfied:0.55<(T1/f)×100<1.40  (4)

where

T1: a distance along the optical axis from an image-side surface of thefirst lens to an object-side surface of the second lens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (4) defines an appropriate range of adistance along the optical axis between the first lens and the secondlens. By satisfying the conditional expression (4), coma aberration andthe astigmatism can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (5) is satisfied:7.50<f2/f5<19.50  (5)

where

f2: a focal length of the second lens, and

f5: a focal length of the fifth lens.

The conditional expression (5) defines an appropriate range ofrefractive powers of the second lens and the fifth lens. By satisfyingthe conditional expression (5), the coma aberration, the astigmatism andthe distortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (6) is satisfied:2.80<(T4/f)×100<9.00  (6)

where

T4: a distance along the optical axis from an image-side surface of thefourth lens to an object-side surface of the fifth lens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (6) defines an appropriate range of adistance along the optical axis between the fourth lens and the fifthlens. By satisfying the conditional expression (6), the astigmatism andthe distortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (7) is satisfied:0.05<T1/T2<0.18  (7)

where

T1: a distance along the optical axis from an image-side surface of thefirst lens to an object-side surface of the second lens, and

T2: a distance along the optical axis from an image-side surface of thesecond lens to an object-side surface of the third lens.

The conditional expression (7) defines an appropriate range of adistance between the first lens and the second lens and a distancebetween the second lens and the third lens. By satisfying theconditional expression (7), difference of the distance between the firstlens and the second lens and the distance between the second lens andthe third lens is suppressed from being large, and the low-profilenessis achieved. Furthermore, by satisfying the conditional expression (7),the coma aberration, the astigmatism and the distortion can be properlycorrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (8) is satisfied:0.70<D3/T3<1.40  (8)

where

D3: a thickness along the optical axis of the third lens, and

T3: a distance along the optical axis from an image-side surface of thethird lens to an object-side surface of the fourth lens.

The conditional expression (8) defines an appropriate range of athickness along the optical axis of the third lens. When a value isbelow the upper limit of the conditional expression (8), the thicknessalong the optical axis of the third lens is suppressed from being toolarge, and air gaps of the object side and the image side of the thirdlens can be easily secured. As a result, the low-profileness can beachieved. On the other hand, when the value is above the lower limit ofthe conditional expression (8), the thickness along the optical axis ofthe third lens is suppressed from being too small, and formability ofthe lens becomes excellent. Furthermore, by satisfying the conditionalexpression (8), the astigmatism and the distortion can be properlycorrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (9) is satisfied:1.80<D4/T4<3.50  (9)

where

D4: a thickness along the optical axis of the fourth lens, and

T4: a distance along the optical axis from an image-side surface of thefourth lens to an object-side surface of the fifth lens.

The conditional expression (9) defines an appropriate range of athickness along the optical axis of the fourth lens. When a value isbelow the upper limit of the conditional expression (9), the thicknessalong the optical axis of the fourth lens is suppressed from being toolarge, and air gaps of the object side and the image side of the fourthlens can be easily secured. As a result, the low-profileness can beachieved. On the other hand, when the value is above the lower limit ofthe conditional expression (9), the thickness along the optical axis ofthe fourth lens is suppressed from being too small, and formability ofthe lens becomes excellent. Furthermore, by satisfying the conditionalexpression (9), the astigmatism, the field curvature and the distortioncan be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (10) is satisfied:0.40<r3/f<1.15  (10)

where

r3: paraxial curvature radius of an object-side surface of the secondlens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (10) defines an appropriate range of theparaxial curvature radius of the object-side surface of the second lens.When a value is below the upper limit of the conditional expression(10), the field curvature can be properly corrected. On the other hand,when the value is above the lower limit of the conditional expression(10), the distortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (11) is satisfied:0.50<r3/r4<1.45  (11)

where

r3: paraxial curvature radius of an object-side surface of the secondlens, and

r4: paraxial curvature radius of an image-side surface of the secondlens.

The conditional expression (11) defines an appropriate range of paraxialcurvature radii of the object-side surface and the image-side surface ofthe second lens. By satisfying the conditional expression (11), theastigmatism and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (12) is satisfied:f2/f<−3.50  (12)

where

f2: a focal length of the second lens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (12) defines an appropriate range ofrefractive power of the second lens. By satisfying the conditionalexpression (12), the distortion is properly corrected and thelow-profileness is achieved.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (13) is satisfied:TTL/EPd≤2.30  (13)

where

TTL: a total track length, and

EPd: an entrance pupil diameter.

The conditional expression (13) defines a relationship between the totaltrack length and the entrance pupil diameter. By satisfying theconditional expression (13), the total track length can be shortened,decrease in light quantity at the peripheral area can be suppressed andan image having sufficient brightness from a center to a peripheral areacan be obtained.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (14) is satisfied:−1.00<(D2/f2)×100<−0.55  (14)

where

D2: a thickness along the optical axis of the second lens, and

f2: a focal length of the second lens.

The conditional expression (14) defines an appropriate range of athickness along the optical axis of the second lens. When a value isbelow the upper limit of the conditional expression (14), the thicknessalong the optical axis of the second lens is suppressed from being toosmall, and the formability of the lens becomes excellent. On the otherhand, when the value is above the lower limit of the conditionalexpression (14), the thickness along the optical axis of the second lensis suppressed from being too large, air gaps on the object side and theimage side of the second lens can be easily secured. As a result, thelow-profileness can be realized. Furthermore, by satisfying theconditional expression (14), the coma aberration and the distortion canbe properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that a below conditional expression (15) is satisfied:0.50<f1/f<1.65  (15)

where

f1: a focal length of the first lens,

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (15) defines an appropriate range of therefractive power of the first lens. When a value is below the upperlimit of the conditional expression (15), positive refractive power ofthe first lens becomes appropriate, and the low-profileness can beachieved. On the other hand, when the value is above the lower limit ofthe conditional expression (15), the spherical aberration, theastigmatism and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration,it is preferable that composite refractive power of the second lens andthe third lens is negative, and more preferable that a below conditionalexpression (16) is satisfied:−13.00<f23/f<−3.50  (16)

where

f23: a composite focal length of the second lens and the third lens, and

f: a focal length of the overall optical system of the imaging lens.

When the composite refractive power of the second lens and the thirdlens is negative, it is favorable for correction of the chromaticaberration. The conditional expression (16) defines an appropriate rangeof the composite refractive power of the second lens and the third lens.When a value is below the upper limit of the conditional expression(16), the negative composite refractive power of the second lens and thethird lens becomes appropriate, and the low-profileness can be achieved.On the other hand, when the value is above the lower limit of theconditional expression (16), the astigmatism and the distortion can beproperly corrected.

According to the imaging lens having the above-described configuration,it is preferable that composite refractive power of the fourth lens andthe fifth lens is positive, and more preferable that a below conditionalexpression (17) is satisfied:45.00<f45/f  (17)

where

f45: a composite focal length of the fourth lens and the fifth lens, and

f: a focal length of the overall optical system of the imaging lens.

When the composite refractive power of the fourth lens and the fifthlens is positive, it is favorable for the low-profileness. Theconditional expression (17) defines an appropriate range of thecomposite refractive power of the fourth lens and the fifth lens. Bysatisfying the conditional expression (17), the astigmatism, the fieldcurvature and the distortion can be properly corrected.

Effect of Invention

According to the present invention, there can be provided an imaginglens with high resolution which satisfies demand of the wide field ofview, the low-profileness and the low F-number in well balance, andproperly corrects aberrations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an imaging lens in Example 1according to the present invention;

FIG. 2 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 1 according to the present invention;

FIG. 3 is a schematic view showing an imaging lens in Example 2according to the present invention;

FIG. 4 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 2 according to the present invention;

FIG. 5 is a schematic view showing an imaging lens in Example 3according to the present invention;

FIG. 6 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 3 according to the present invention;

FIG. 7 is a schematic view showing an imaging lens in Example 4according to the present invention; and

FIG. 8 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 4 according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, the preferred embodiments of the present invention will bedescribed in detail referring to the accompanying drawings.

FIGS. 1, 3, 5 and 7 are schematic views of the imaging lenses inExamples 1 to 4 according to the embodiments of the present invention,respectively.

As shown in FIG. 1, the imaging lens according to the present embodimentcomprises, in order from an object side to an image side, a first lensL1 having a convex surface facing the object side and positiverefractive power near an optical axis X, a second lens L2 havingnegative refractive power near the optical axis X, a third lens L3having aspheric surfaces on both sides, a fourth lens L4, and a fifthlens L5 having a concave surface facing the image side and the negativerefractive power near the optical axis X. An image-side surface of thefifth lens L5 is formed as an aspheric surface having at least one polepoint in a position off the optical axis X.

A filter IR such as an IR cut filter and a cover glass are arrangedbetween the fifth lens L5 and an image plane IMG (namely, the imageplane of an image sensor). The filter IR is omissible.

By arranging an aperture stop ST on the object side of the first lensL1, correction of aberrations and control of an incident angle of thelight ray of high image height to the image sensor become facilitated.

The first lens L1 has the positive refractive power and has a meniscusshape having a convex surface facing the object side and a concavesurface facing the image side near the optical axis X. Therefore,spherical aberration, astigmatism and distortion can be properlycorrected.

The second lens L2 has the negative refractive power and has a meniscusshape having a convex surface facing the object side and a concavesurface facing the image side near the optical axis X. Therefore, thespherical aberration, chromatic aberration, the astigmatism and thedistortion can be properly corrected.

The third lens L3 has plane surfaces facing the object side and theimage side near the optical axis X and substantially has no refractivepower near the optical axis X. In this case, the astigmatism, the fieldcurvature and the distortion at a peripheral area can be properlycorrected by the aspheric surfaces on both sides without affecting afocal length of the overall optical system of the imaging lens.

The fourth lens L4 has the positive refractive power and has a meniscusshape having a concave surface facing the object side and a convexsurface facing the image side near the optical axis X. Therefore, alight ray incident angle to the fourth lens L4 becomes appropriate, andthe astigmatism, the field curvature and the distortion can be properlycorrected.

The fifth lens L5 has the negative refractive power and has a meniscusshape having a convex surface facing the object side and a concavesurface facing the image side near the optical axis X. Therefore, thechromatic aberration, the astigmatism, the field curvature and thedistortion can be properly corrected.

An object-side surface and an image-side surface of the fifth lens L5are formed as the aspheric surfaces having at least one pole point in aposition off the optical axis X. Therefore, the field curvature and thedistortion can be properly corrected and a light ray incident angle toan image sensor can be properly controlled.

Regarding the imaging lens according to the present embodiments, it ispreferable that all lenses of the first lens L1 to the fifth lens L5 aresingle lenses. Configuration only with the single lenses can frequentlyuse the aspheric surfaces. In the present embodiments, all lens surfacesare formed as appropriate aspheric surfaces, and the aberrations arefavorably corrected. Furthermore, in comparison with the case in which acemented lens is used, workload is reduced, and manufacturing in lowcost becomes possible.

Furthermore, the imaging lens according to the present embodiments makesmanufacturing facilitated by using a plastic material for all of thelenses, and mass production in a low cost can be realized.

The material applied to the lens is not limited to the plastic material.By using glass material, further high performance may be aimed. It ispreferable that all of lens-surfaces are formed as aspheric surfaces,however, spherical surfaces easy to be manufactured may be adopted inaccordance with required performance.

The imaging lens according to the present embodiments shows preferableeffect by satisfying the below conditional expressions (1) to (17).0.70<vd3/vd4<1.30  (1)0.40<r2/f<1.20  (2)2.20<r9/f<6.00  (3)0.55<(T1/f)×100<1.40  (4)7.50<f2/f5<19.50  (5)2.80<(T4/f)×100<9.00  (6)0.05<T1/T2<0.18  (7)0.70<D3/T3<1.40  (8)1.80<D4/T4<3.50  (9)0.40<r3/f<1.15  (10)0.50<r3/r4<1.45  (11)f2/f<−3.50  (12)TTL/EPd≤2.30  (13)−1.00<(D2/f2)×100<−0.55  (14)0.50<f1/f<1.65  (15)−13.00<f23/f<−3.50  (16)45.00<f45/f  (17)

where

vd3: an abbe number at d-ray of the third lens L3,

vd4: an abbe number at d-ray of the fourth lens L4,

D2: a thickness along the optical axis X of the second lens L2,

D3: a thickness along the optical axis X of the third lens L3,

D4: a thickness along the optical axis X of the fourth lens L4,

T1: a distance along the optical axis X from an image-side surface ofthe first lens L1 to an object-side surface of the second lens L2,

T2: a distance along the optical axis X from an image-side surface ofthe second lens L2 to an object-side surface of the third lens L3,

T3: a distance along the optical axis X from an image-side surface ofthe third lens L3 to an object-side surface of the fourth lens L4,

T4: a distance along the optical axis X from an image-side surface ofthe fourth lens L4 to an object-side surface of the fifth lens L5,

TTL: a total track length,

EPd: an entrance pupil diameter,

f: a focal length of the overall optical system of the imaging lens,

f1: a focal length of the first lens L1,

f2: a focal length of the second lens L2,

f5: a focal length of the fifth lens L5,

f23: a composite focal length of the second lens L2 and the third lensL3,

f45: a composite focal length of the fourth lens L4 and the fifth lensL5,

r2: paraxial curvature radius of an image-side surface of the first lensL1,

r3: paraxial curvature radius of an object-side surface of the secondlens L2,

r4: paraxial curvature radius of an image-side surface of the secondlens L2, and

r9: paraxial curvature radius of an object-side surface of the fifthlens L5.

It is not necessary to satisfy the above all conditional expressions,and by satisfying the conditional expression individually, operationaladvantage corresponding to each conditional expression can be obtained.

The imaging lens according to the present embodiments shows furtherpreferable effect by satisfying the below conditional expressions (1a)to (17a).0.85<vd3/vd4<1.15  (1a)0.65<r2/f<1.05  (2a)2.75<r9/f<5.00  (3a)0.85<(T1/f)×100<1.25  (4a)9.00<f2/f5<16.00  (5a)4.00<(T4/f)×100<7.50  (6a)0.08<T1/T2<0.14  (7a)0.90<D3/T3<1.25  (8a)2.20<D4/T4<3.20  (9a)0.65<r3/f<1.00  (10a)0.85<r3/r4<1.30  (11a)−13.00<f2/f<−5.00  (12a)TTL/EPd≤2.20  (13a)−0.90<(D2/f2)×100<−0.65  (14a)0.80<f1/f<1.35  (15a)−10.50<f23/f<−5.00  (16a)70.00<f45/f  (17a)

The signs in the above conditional expressions have the same meanings asthose in the paragraph before the preceding paragraph.

In this embodiment, the aspheric shapes of the aspheric surfaces of thelens are expressed by Equation 1, where Z denotes an axis in the opticalaxis direction, H denotes a height perpendicular to the optical axis, Rdenotes a paraxial curvature radius, k denotes a conic constant, and A4,A6, A8, A10, A12, A14, A16, A18 and A20 denote aspheric surfacecoefficients.

$\begin{matrix}{Z = {\frac{\frac{H^{2}}{R}}{1 + \sqrt{1 - {\left( {k + 1} \right)\frac{H^{2}}{R^{2}}}}} + {A_{4}H^{4}} + {A_{6}H^{6}} + {A_{8}H^{8}} + {A_{10}H^{10}} + {A_{12}H^{12}} + {A_{14}H^{14}} + {A_{16}H^{16}} + {A_{18}H^{18}} + {A_{20}H^{20}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Next, examples of the imaging lens according to this embodiment will beexplained. In each example, f denotes the focal length of the overalloptical system of the imaging lens, Fno denotes an F-number, ω denotes ahalf field of view, ih denotes a maximum image height, and TTL denotes atotal track length. Additionally, i denotes surface number counted fromthe object side, r denotes the paraxial curvature radius, d denotes thedistance of lenses along the optical axis (surface distance), Nd denotesa refractive index at d-ray (reference wavelength), and vd denotes anabbe number at d-ray. As for aspheric surfaces, an asterisk (*) is addedafter surface number i.

Example 1

The basic lens data is shown below in Table 1.

TABLE 1 Example 1 Unit mm f = 3.63 i h = 2.93 Fno = 1.80 TTL = 4.24 ω(°)= 38.5 Surface Data Surface Curvature Surface Refractive Abbe Number IRadius r Distance d Index Nd Number νd (Object) Infinity Infinity 1(Stop) Infinity −0.3598  2* 1.3819 0.6210 1.544 55.86 (νd1)  3* 3.19570.0403  4* 2.8925 0.2100 1.671 19.48 (νd2)  5* 2.4609 0.3636  6*Inifnity 0.3834 1.535 55.66 (νd3)  7* Inifnity 0.3582  8* −5.0815 0.55241.544 55.86 (νd4)  9* −1.2094 0.2150 10* 14.3437 0.4553 1.535 55.66(νd5) 11* 1.1430 0.4000 18  Infinity 0.2100 1.517 64.20 19  Infinity0.4996 Image Plane Infinity Constituent Lens Data Start Focal CompositeEntrance pupil Lens Surface Length Focal Length diameter 1 2 3.991 f23−30.526 EPd 2.017 2 4 −30.526 f45 732.341 3 6 Infinity 4 8 2.776 5 10−2.351 Aspheric Surface Data Second Third Fourth Fifth Sixth SurfaceSurface Surface Surface Surface k   1.094850E−01   5.159893E−01  4.336670E−01 −7.250467E−01 −1.000000E+00 A4   1.963090E−02−3.478435E−01 −3.932523E−01   1.597878E−01   1.712448E−02 A6−1.965316E−01 −1.585724E+00 −2.014276E+00 −4.941724E+00 −2.796328E+00 A8  8.445733E−01   1.495298E+01   1.972350E+01   4.367168E+01  1.981598E+01 A10 −1.958527E+00 −5.598312E+01 −7.580828E+01−2.110428E+02 −8.596558E+01 A12   2.045365E+00   1.243143E+02  1.738658E+02   6.382435E+02   2.345025E+02 A14   2.469822E−01−1.740764E+02 −2.520192E+02 −1.227197E+03 −4.047148E+02 A16−2.818170E+00   1.504530E+02   2.276889E+02   1.456250E+03  4.287236E+02 A18   2.554451E+00 −7.324215E+01 −1.159880E+02−9.716176E+02 −2.548004E+02 A20 −7.714514E−01   1.533838E+01  2.547475E+01   2.789419E+02   6.547661E+01 Seventh Eighth Ninth TenthEleventh Surface Surface Surface Surface Surface k −1.000000E+00  0.000000E+00 −2.466285E+00   2.171846E+01 −5.799982E+00 A4−1.395394E−01   7.600523E−02   7.126290E−02 −3.359768E−01 −2.172774E−01A6   1.574205E−01 −3.141305E−01 −2.638511E−01   1.605923E−01  1.843677E−01 A8 −1.781540E+00   4.714353E−01   3.940781E−01  1.777543E−02 −1.200356E−01 A10   6.682577E+00 −8.855708E−01−3.913931E−01 −5.011791E−02   5 542673E−02 A12 −1.425418E+01  1.521222E+00   2.656622E−01   2.664113E−02 −1.752291E−02 A14  1.842587E+01 −1.851934E+00 −9.018800E−02 −7.856430E−03   3.617590E−03A16 −1.434340E+01   1.376567E+00   1.554599E−03   1.409900E−03−4.569088E−04 A18   8.219672E+00 −5.480955E−01   6.793580E−03−1.409780E−04   3.138665E−05 A20 −1.142116E+00   8.920000E−02−1.211420E−03   5.992440E−06 −8.704106E−07

The imaging lens in Example 1 satisfies conditional expressions (1) to(17) as shown in Table 5.

FIG. 2 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 1. The spherical aberration diagramshows the amount of aberration at each wavelength of F-ray (486 nm),d-ray (588 nm), and C-ray (656 nm). The astigmatism diagram shows theamount of aberration at d-ray on a sagittal image surface S (solid line)and on tangential image surface T (broken line), respectively (same asFIGS. 4, 6 and 8). As shown in FIG. 2, each aberration is correctedexcellently.

Example 2

The basic lens data is shown below in Table 2.

TABLE 2 Example 2 Unit mm f = 3.63 i h = 2.93 Fno = 1.80 TTL = 4.24 ω(°)= 38.5 Surface Data Surface Curvature Surface Refractive Abbe Number IRadius r Distance d Index Nd Number νd (Object) Infinity Infinity 1(Stop) Infinity −0.3535  2*    1.3731 0.6195 1.544 55.86 (νd1)  3*    32879 0.0400  4*    3.0454 0.2050 1.671 19.48 (νd2)  5*    2.5197 0.3584 6* Inifnity 0.3929 1.535 55.66 (νd3)  7* Inifnity 0.3716  8*  −4.82780.5599 1.544 55.86 (νd3)  9*  −1.1754 0.2007 10*   12.5693 0.4513 1.53555.66 (νd5) 11*    1.1042 0.4000 18  Infinity 0.2100 1.517 64.20 19 Infinity 0.4994 Image Plane Infinity Constituent Lens Data Start FocalComposite Entrance pupil Lens Surface Length Focal Length diameter 1 23.888 f23 −25.778 EPd 2.015 2 4 −25.778 f45 12456.950 3 6 Infinity 4 82.711 5 10 −2.295 Aspheric Surface Data Second Third Fourth Fifth SixthSurface Surface Surface Surface Surface k   8.738263E−02   5.159893E−01  9.534546E−01 −1.066967E+00 −1.000000E+00 A4 −1.484794E−02−3.940857E−01 −4.853926E−01   2.518315E−02 −2.822121E−02 A6  2.343453E−01 −1 201658E+00 −1.068783E+00 −3.161572E+00 −2.410789E+00A8 −1.914350E+00   1.374961E+01   1.484948E+01   3.120328E+01  1.827395E+01 A10   8.370375E+00 −5.497832E+01 −5.981522E+01−1.585349E+02 −8.460972E+01 A12 −2.172061E+01   1.283613E+02  1.388654E+02   5.019304E+02   2.463512E+02 A14   3.423647E+01−1.876625E+02 −2.013390E+02 −1.011367E+03 −4.537118E+02 A16−3.224610E+01   1.683651E+02   1.791137E+02   1.259282E+03  5.126048E+02 A18   1.666603E+01 −8.464390E+01 −8.909230E+01−8.823785E+02 −3.245385E+02 A20 −3.649447E+00   1.823811E+01  1.889822E+01   2.662613E+02   8.857284E+01 Seventh Eighth Ninth TenthEleventh Surface Surface Surface Surface Surface k −1.000000E+00  0.000000E+00 −2.314011E+00   2.171846E+01 −5.799982E+00 A4−1.413775E−01   6.605460E−02   7.177787E−02 −3.499849E−01 −2.135550E−01A6   8.793969E−02 −3.753137E−01 −2.777709E−01   2.124389E−01  1.858305E−01 A8 −1.197918E+00   7.248172E−01   4.540283E−01−3.932331E−02 −1.223597E−01 A10   4.799631E+00 −1.281163E+00−5.097521E−01 −1.873234E−02   5.682121E−02 A12 −1.092398E+01  1.652152E+00   3.921725E−01   1.590078E−02 −1.789417E−02 A14  1.511163E+01 −1.460787E+00 −1.732363E−01 −5.457216E−03   3 698436E−03A16 −1.260304E+01   8.268979E−01   3.529859E−02   1.030084E−03−4.699846E−04 A18   5.846298E+00 −2.642727E−01 −9.049300E−04−1.029953E−04   3.282584E−05 A20 −1.142116E+00   3.620000E−02−4.676916E−04   4.236171E−06 −9.463898E−07

The imaging lens in Example 2 satisfies conditional expressions (1) to(17) as shown in Table 5.

FIG. 4 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 2. As shown in FIG. 4, eachaberration is corrected excellently.

Example 3

The basic lens data is shown below in Table 3.

TABLE 3 Example 3 Unit mm f = 3.63 i h = 2.93 Fno = 1.80 TTL = 4.24 ω(°)= 38.5 Surface Data Surface Curvature Surface Refractive Abbe Number IRadius r Distance d Index Nd Number νd (Object) Infinity Infinity 1(Stop) Infinity −0.3576  2*   1.3712   0.6187 1.544 55.86 (νd1)  3*  3.2598   0.0408  4*   3.0691   0.2050 1.671 19.48 (νd2)  5*   2.5432  0 3584  6* Inifnity   0.3856 1.535 55.66 (νd3)  7* Inifnity   0.3673 8* −4 4872   0.5615 1.544 55.86 (νd4)  9* −1.1532   0.2030 10*  11.6591    0.4437 1.535 55.66 (νd5) 11*   1.0983   0.4000 18  Infinity  0.2100 1.517 64.20 19  Infinity   0.5145 Image Plane InfinityConstituent Lens Data Start Focal Composite Entrance pupil Lens SurfaceLength Focal Length diameter 1 2 3.898 f23 −26.207 EPd 2.015 2 4 −26.207f45 359.519 3 6 Infinity 4 8 2.692 5 10 −2.301 Aspheric Surface DataSecond Third Fourth Fifth Sixth Surface Surface Surface Surface Surfacek   8.383528E−02   5.159893E−01   1.066306E+00 −9.814557E−01−1.000000E+00 A4 −1.894990E−02 −3.616493E−01 −4.480912E−01  1.629409E−02 −4.668614E−02 A6   2.929541E−01 −1.553735E+00−1.458195E+00 −2.909055E+00 −1.922501E+00 A8 −2.344762E+00  1.557759E+01   1.680218E+01   2.832357E+01   1.318006E+01 A10  1.015402E+01 −6.075976E+01 −6.541353E+01 −1.408133E+02 −5.577081E+01A12 −2.619725E+01   1.399965E+02   1.482942E+02   4.376881E+02  1.492152E+02 A14   4.116742E+01 −2.025015E+02 −2.100304E+02−8.694893E+02 −2.538363E+02 A16 −3.870242E+01   1.798641E+02  1.821384E+02   1.071270E+03   2.662811E+02 A18   1.997579E+01−8.952364E+01 −8.800716E+01 −7.449257E+02 −1.576897E+02 A20−4.365525E+00   1.909439E+01   1.804471E+01   2.236398E+02  4.083573E+01 Seventh Eighth Ninth Tenth Eleventh Surface SurfaceSurface Surface Surface k −1.000000E+00   0.000000E+00 −2.302780E+00  2.171846E+01 −5.799983E+00 A4 −1.218317E−01   7.516854E−02  7.646362E−02 −3.392410E−01 −2.115185E−01 A6 −8.431598E−02−4.593756E−01 −2.902381E−01   1.974353E−01   1.823209E−01 A8−3.223502E−01   1.082886E+00   4.568366E−01 −2.791666E−02 −1.195869E−01A10   2.187057E+00 −2.183614E+00 −4.828303E−01 −2.545613E−02  5.527455E−02 A12 −6.304358E+00   3.037362E+00   3.356138E−01  1.881360E−02 −1.747832E−02 A14   1.034338E+01 −2.777325E+00−1.188046E−01 −6.299714E−03   3.617663E−03 A16 −9.963075E+00  1.576681E+00   7.756817E−03   1.181492E−03 −4.603588E−04 A18  5.244292E+00 −4.958395E−01   6.155387E−03 −1.183193E−04   3.216932E−05A20 −1.142116E+00   6.580000E−02 −1.191835E−03   4.907140E−06−9.261991E−07

The imaging lens in Example 3 satisfies conditional expressions (1) to(17) as shown in Table 5.

FIG. 6 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 3. As shown in FIG. 6, eachaberration is corrected excellently.

Example 4

The basic lens data is shown below in Table 4.

TABLE 4 Example 4 Unit mm f = 3.63 i h = 2.93 Fno = 1.80 TTL = 4.24 ω(°)= 38.5 Surface Data Surface Curvature Surface Refractive Abbe Number IRadius r Distance d Index Nd Number νd (Object) Infinity Infinity 1(Stop) Infinity −0.3545  2* 1.3717 0.6198 1.544 55.86 (νd1)  3* 3.28690.0400  4* 3.0632 0.2050 1.671 19.48 (νd2)  5* 2.5296 0.3586  6*Inifnity 0.3945 1.535 55.66 (νd3)  7* Inifnity 0.3889  8* −4.7497 0.56051.544 55.86 (νd4)  9* −1.1692 0.2000 10* 12.5129 0.4497 1.535 55.66(νd5) 11* 1.1010 0.4000 18  Infinity 0.2100 1.517 64.20 19  Infinity0.5015 Image Plane Infinity Constituent Lens Data Start Focal CompositeEntrance pupil Lens Surface Length Focal Length diameter 1 2 3.882 f23−25.572 EPd 2.014 2 4 −25.572 f45 3895.122 3 6 Infinity 4 8 2.701 5 10−2.289 Aspheric Surface Data Second Third Fourth Fifth Sixth SurfaceSurface Surface Surface Surface k   8.649794E−02   5.159893E−01  9.875174E−01 −1.103670E+00 −1.000000E+00 A4 −1.360465E−02−3.742858E−01 −4.641731E−01   1.276310E−02 −2.345572E−02 A6  2.106143E−01 −1.490420E+00 −1.396205E+00 −2.905771E+00 −2.564865E+00A8 −1 728106E+00   1.566564E+01   1.719896E+01   2.847458E+01  1.987389E+01 A10   7.606057E+00 −6.232724E+01 −6.958586E+01−1.418627E+02 −9.324960E+01 A12 −1.988381E+01   1.457249E+02  1.639847E+02   4.402548E+02   2.735745E+02 A14   3.154501E+01−2.132905E+02 −2.417780E+02 −8.706507E+02 −5.057554E+02 A16−2.987138E+01   1.913685E+02   2.187706E+02   1.065753E+03  5.721784E+02 A18   1.550235E+01 −9.612243E+01 −1.107379E+02−7.353614E+02 −3.621831E+02 A20 −3.405623E+00   2.067931E+01  2.393955E+01   2.189109E+02   9.868621E+01 Seventh Eighth Ninth TenthEleventh Surface Surface Surface Surface Surface k −1.000000E+00  0.000000E+00 −2.295281E+00   2.171846E+01 −5.799982E+00 A4−1.242622E−01   7.646192E−02   7.088234E−02 −3.537949E−01 −2.159761E−01A6 −5.128998E−02 −4.682300E−01 −2.701391E−01   2.239803E−01  1.903744E−01 A8 −5.770820E−01   1.109443E+00   4.258682E−01−5.047134E−02 −1.283921E−01 A10   3.180935E+00 −2.190300E+00−4.463583E−01 −1.415896E−02   5.888501E−02 A12 −8.386006E+00  2.967309E+00   3.122519E−01   1.543293E−02 −1.854378E−02 A14  1.276300E+01 −2.642098E+00 −1.161675E−01 −5.737179E−03   3.822763E−03A16 −1.142003E+01   1.464422E+00   1.213908E−02   1.142934E−03−4.833352E−04 A18   5.596458E+00 −4.520453E−01   4.102200E−03−1.195857E−04   3.346811E−05 A20 −1.143000E+00   5.913427E−02−9.174172E−04   5.141248E−05 −9.505715E−07

The imaging lens in Example 4 satisfies conditional expressions (1) to(17) as shown in Table 5.

FIG. 8 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 4. As shown in FIG. 8, eachaberration is corrected excellently.

In table 5, values of conditional expressions (1) to (17) related to theExamples 1 to 4 are shown.

TABLE 5 Conditional expression Example1 Example2 Example3 Example4  (1)νd3/νd4 1.00 1.00 1.00 1.00  (2) r2/f 0.80 0.91 0.90 0.81  (3) r9/f 3.953.47 3.21 3.45  (4) (T1/f) × 100 1.11 1.10 1.12 1.10  (5) f2/f5 12.9911.23 11.38 11.17  (6) (T4/f) × 100 5.92 5.53 5.60 5.52  (7) T1/T2 0.110.11 0.11 0.11  (8) D3/T2 1.07 1.06 1.05 1.07  (9) D4/T4 2.57 2.79 2.772.80 (10) r3/f 0.80 0.84 0.85 0.84 (11) r3/r4 1.10 1.21 1.21 1.21 (12)f2/f −8.41 −7.11 −7.23 −7.05 (13) TTL/EPd 2.10 2.10 2.10 2.10 (14)(D2/f2) × 100 −0.69 −0.80 −0.78 −0.80 (15) f1/f 1.10 1.07 1.07 1.07 (16)f23/f −8.41 −7.11 −7.23 −7.05 (17) f45/f 201.68 3435.16 99.13 1074.25

When the imaging lens according to the present invention is adopted to aproduct with the camera function, there is realized contribution to thewide field of view, the low-profileness and the low F-number of thecamera and also high performance thereof.

DESCRIPTION OF REFERENCE NUMERALS

-   ST: an aperture stop-   L1: a first lens-   L2: a second lens-   L3: a third lens-   L4: a fourth lens-   L5: a fifth lens-   ih: a maximum image height-   IR: a filter-   IMG: an imaging plane

What is claimed is:
 1. An imaging lens comprising in order from anobject side to an image side, a first lens having a convex surfacefacing the object side and positive refractive power near an opticalaxis, a second lens having negative refractive power near the opticalaxis, a third lens having aspheric surfaces on both sides, a fourthlens, and a fifth lens having a concave surface facing the image sideand the negative refractive power near the optical axis, wherein animage-side surface of said fifth lens is formed as an aspheric surfacehaving at least one pole point in a position off the optical axis, animage-side surface of said first lens is a concave surface facing theimage side near the optical axis and below conditional expressions (4),(5) and (10) are satisfied:0.55<(T1/f)×100<1.40  (4)7.50<f2/f5<19.50  (5)0.40<r3/f<1.15  (10) where r3: paraxial curvature radius of anobject-side surface of the second lens, T1: a distance along the opticalaxis from an image-side surface of the first lens to an object-sidesurface of the second lens, f: a focal length of the overall opticalsystem of the imaging lens, f2: a focal length of the second lens, andf5: a focal length of the fifth lens.
 2. The imaging lens according toclaim 1, wherein an object-side surface of said fifth lens is a convexsurface facing the object side near the optical axis.
 3. The imaginglens according to claim 2, wherein a below conditional expression (1) issatisfied:0.70<vd3/vd4<1.30  (1) where vd3: an abbe number at d-ray of the thirdlens, and vd4: an abbe number at d-ray of the fourth lens.
 4. Theimaging lens according to claim 2, wherein a below conditionalexpression (2) is satisfied:0.40<r2/f<1.20  (2) where r2: paraxial curvature radius of an image-sidesurface of the first lens, and f: a focal length of the overall opticalsystem of the imaging lens.
 5. The imaging lens according to claim 2,wherein a below conditional expression (3) is satisfied:2.20<r9/f<6.00  (3) where r9: paraxial curvature radius of anobject-side surface of the fifth lens, and f: a focal length of theoverall optical system of the imaging lens.
 6. The imaging lensaccording to claim 2, wherein a below conditional expression (11) issatisfied:0.50<r3/r4<1.45  (11) where r3: paraxial curvature radius of anobject-side surface of the second lens, and r4: paraxial curvatureradius of an image-side surface of the second lens.
 7. The imaging lensaccording to claim 2, wherein a below conditional expression (12) issatisfied:f2/f<−3.50  (12) where f2: a focal length of the second lens, and f: afocal length of the overall optical system of the imaging lens.
 8. Theimaging lens according to claim 2, wherein a below conditionalexpression (13) is satisfied:TTL/EPd<2.30  (13) where EPd: an entrance pupil diameter, and TTL: atotal track length.